The complexity of the lung necessitates simplification before biochemical methods can be fully utilized to understand the maintenance of lung structure and function in health and disease. One approach to this problem is by utilizing cell culture methods to isolate and maintain homogeneous populations of lung cells. These methods are being used to evaluate lung collagen synthesis, the maintenance of the differentiated state in culture, glycosaminoglycan synthesis, biochemical identification of cells in culture, mechanisms of collagen degradation, hereditary disorders of connective tissue, compostion of lung connective tissue, maintenance of lung cells from patients with pulmonary fibrosis, immunologic interactions in fibrotic disease and in vitro models of environmental lung injury.